1. Technical Field
The present invention is generally directed to a filter assembly for use in a dust collector. In particular, the present invention is directed to a filter cartridge structure and apparatus for mounting and supporting the filter cartridge in the dust collector.
2. Description of the Prior Art
Dust collectors, such as baghouses, for filtering particulate-laden air are well known. A typical baghouse has a housing with a dirty air chamber and a clean air chamber. The two chambers are separated by sheet metal, commonly referred to as a tubesheet. The tubesheet has a number of openings through which cylindrical filters, such as bags or cartridges, typically extend. The filters are suspended by the tubesheet and extend into the dirty air chamber. Particulate-laden air is introduced into the dirty air chamber. The air passes through the filters and through the openings in the tubesheet into the clean air chamber. The particulates are separated from the air flow by the filters. The filtered air is exhausted from the clean air chamber or directed for other uses.
Important in the design of a filter bag or filter cartridge and associated support structure is that a good seal must exist between the filter and the supporting tubesheet. If a good seal does not exist, particulate-laden air may leak around the filter, through the tubesheet opening and into the clean air chamber. This leakage results in the undesirable situation of having particulate-laden air in the clean air chamber.
Numerous attempts have been made to develop a baghouse filter and support structure for attaching a filter element to a baghouse tubesheet. U.S. Pat. Nos. 4,292,057; 4,424,070; 4,436,536; 4,443,237 and 4,445,915 are representative examples of prior art filter elements and attachment structure. U.S. Pat. No. 5,632,791 discloses a flexible sleeve molded from relatively soft urethane material that directly engages a surface defining an opening in the tubesheet. U.S. Pat. No. 5,746,792 discloses a metal mounting collar that is engagable with a flexible snapband for sealing against a tubesheet.
In spite of significant efforts at solving the problems and disadvantages with prior art filters, the prior art filters and associated support structure tend to be complex, which adds to the cost of the filter and installation in the baghouse. The prior art filters also have not been altogether satisfactory in preventing particulate-laden air from leaking from the dirty air chamber, through the tubesheet opening, and into the clean air chamber. The mounting and sealing of filters within a baghouse tubesheet remains one of the most time-consuming and expensive operations in the manufacture of baghouses and in the replacement of filters.
U.S. patent application Ser. No. 10/448,693 discloses a filter cartridge and support structure for use in a baghouse having a tubesheet with openings. A flexible snapband with a metal spring component and fabric cover is biased into engagement with a surface of the opening in the tubesheet. The snapband receives a portion of the filter cartridge. A rigid non-metallic tubular mounting collar is integrally formed with filter media. The mounting collar includes a pair of longitudinally spaced continuous projections that extend radially outward. The mounting collar is adapted to be positioned within the snapband and engage surfaces of the snapband to effect sealing engagement of the snapband against surfaces of the opening in the tubesheet.
Yet another known attempt at a baghouse support and seal structure involves the use of a rubber grommet having a substantially C-shaped cross-section. The grommet is installed in a tubesheet opening and receives a metal ferrule. During insertion of the ferrule into the grommet, friction from relative movement therebetween tends to pull or roll the grommet out of position. The out-of-position grommet may not provide an effective seal with the tubesheet and ferrule.
Prior art filter mounting systems that incorporate metal mounting collars can be expensive to manufacture and take a relatively long time to fabricate. Snapbands are relatively expensive to manufacture, have relatively small tolerance of opening that they can properly fit and variations in cover fabric thickness makes it difficult to produce consistent finished sizes. Accordingly, the need exists for a filter and mounting systems that are inexpensive, can be quickly manufactured, easy to install and replace in a baghouse and that maintain a good seal. The present invention fills these needs and overcomes the disadvantages of the prior art filter mounting systems.